1. Field of the Invention
The present invention relates to a collective optical coupling method and device, which consists in transferring an electromagnetic wave from an active component such as a laser to a guiding medium such as an optical fiber, or from one guiding medium to another guiding medium.
The field of the invention is that of optical telecommunications and more particularly that of distribution networks which concern short-distance connections and require considerable effort in terms of cost as regards both infrastructures and terminal components. In the field of telecommunications, the wave-length is usually 1.3 or 1.55 .mu..
The joining of optoelectronic modules, called optical coupling, constitutes an operation whose cost needs to be reduced. One solution consists in treating this operation collectively. There are two difficulties: on the one hand, there is the difficulty associated with the mismatch of the shape and size of the optical modes of the elements to be coupled and, on the other hand, the difficulty of positioning them with submicron precision.
This is because the coupled power drops by 1 dB when positioning departs from the optimum position, in the plane perpendicular to the optical axis, by a distance less than 1 micron and along the optical axis by a few microns (.mu.). Dynamic positioning of the elements to be coupled is known, i.e. adjusting the positioning in real time depending on the degree of coupling. However, passive assembly between linear arrays of components and combs of fibers, which consists in positioning the various elements without supplying the components, is difficult to carry out.
2. Description of the Related Art
To solve the problem of laser-fiber coupling, the use of a microlens has been proposed. K. Shiraishi et al. have proposed, in particular, a lens consisting of a section of coreless fiber having a hemispherical end, obtained by micromachining, this section being fusion spliced to a single-mode fiber whose core has been locally widened by heating. The degrees of coupling obtained have severe positioning tolerances. These solutions are complex to implement and difficult to make compatible with a collective treatment on fiber ribbons, for example.